DPL: reduce helpers for makeHolder / makeHolderTypes

[ktf]

DPL: reduce helpers for makeHolder / makeHolderTypes

C++20 allows simplifying the enumeration.

[alibuild]

Error while checking build/O2/fullCI for 0da3c1e at 2024-02-06 10:29:

## sw/BUILD/O2-latest/log
c++: error: unrecognized command-line option '--rtlib=compiler-rt'
c++: error: unrecognized command-line option '--rtlib=compiler-rt'


## sw/BUILD/O2-full-system-test-latest/log
command alien-token-init had nonzero exit code 2


## sw/BUILD/o2checkcode-latest/log
--
========== List of errors found ==========
++ GRERR=0
++ grep -v clang-diagnostic-error error-log.txt
++ grep ' error:'
++ GRERR=1
++ [[ 1 == 0 ]]
++ mkdir -p /sw/INSTALLROOT/bbba6a11e7475a6e61f38357d3bc525726498ef5/slc8_x86-64/o2checkcode/1.0-local1533/etc/modulefiles
++ cat
--

Full log here.

[ktf]

Provides a bit of speedup and reduces unneeded complexity. Tested on hyperloop as well, merging.